Estimation under parametric modeling assumptions is studied in [1]}, and under an assumption that the effect is nonnegative in [2]}. Set identifiability of the average treatment response is discussed in [3]} for a catalog of possible modeling assumptions. The definition and estimation of vaccine-specific effects is an active field, whose breadth is beyond our scope; we refer to [4]} for a recent discussion. Interference between units in observational studies is also an active area of research, and we refer to [5]} and [6]}. Many examples of published experiments involving interference are described in the review article [7]}. [8]} considers experiments in the presence of market equilibirum forces. A precursor to the ideas of this paper can be found in a technical report [9]}, which proposes the estimand (REF ) but without generalization to regression, weighting, or matching.
